Interested to find this as I was searching for a similar Gadgetbridge error connecting to the Bangle.js2. Mine says 'Malformed JSON from Bangle.js: No value for status'. This appears on connection.
My firmware and Gadgetbridge version are up to date, and message connection works OK (I can run most of the tests for connecting, e.g. call and message handling). But the data viewing options show now data (though the watch has plenty!) and the live measurement (heart icon) just spins the wheel with 'MEASURING' message.
I've tried suggestions above, but all the resets and reloads don't seem to do anything.
Grateful for any ideas! Thanks.